Abstract The use of writing to interact with others is of critical importance to persons with severe physical impairments (SPI) and persons with severe speech and physical impairments (SSPI). For these people, written communication tools such as email, texting, and social media play essential roles in supporting social closeness, the exchange of information with others, and exercising self-determination. Many people with SPI, however, experience difficulty both in generating and in editing text using traditional onscreen keyboards. Our Phase 1 research has two goals. The first goal is to correct letter-targeting and spelling errors when a person uses an alternative input method to write. To accomplish this goal we will create and evaluate an input-correction algorithm that recognizes input errors and may increase the writing rate of people with SPI who use scanning as their text input method. Our second goal is to address text-editing challenges when using scanning to correct composition errors (e.g., inserting missing words). To accomplish this goal we will use the language model within our onscreen keyboard to predict the location of composition errors within the writer?s recent text. When the writer indicates that they want to edit their text, the onscreen keyboard will create an ?error prediction list? that replaces the word prediction list available when the writer is composing text. The error prediction algorithm will evaluate the text created by the writer and predict the five most likely locations of errors within the text. When the writer selects one of the predictions, the cursor will jump to the associated location within the text to ease the process of editing. We will evaluate the effectiveness of the error correction algorithms three ways: mathematically, using an Alternating Treatment Design, and through evaluation by assistive technology (AT) experts. We will establish feasibility if our algorithms (1) permit faster scanning rates, (2) correct a substantial number of errors, and (3) AT experts rate the technology as having important benefit.